The present relates to flame-retardant expandable polymers and to polymer foams and to the use thereof. These flame-retardant expandable polymers and polymer foams can be contained in one or several pressurized containers. According to the present, at least one of the following phosphorus compounds is used as a flame retardant: phosphorus compound according to formula (Ia): (Ia) 10-hydroxy-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-OH); or the salts thereof according to formula (Ib): (Ib) (DOPO-OR); or the ring-opened hydrolysates thereof according to formula (Ic): (Ic).